On the origin of the hump structure in the in-plane optical conductivity of high Tc cuprates based on a SU(2) slave-boson theory

TL;DR

This paper uses an improved SU(2) slave-boson theory to analyze the in-plane optical conductivity of high Tc cuprates, revealing the origins of the hump structure and its dependence on doping and temperature.

Contribution

It introduces an enhanced SU(2) slave-boson approach that accounts for phase and amplitude fluctuations, improving understanding of optical conductivity features in high Tc cuprates.

Findings

Mid-infrared hump originates from short-range antiferromagnetic spin fluctuations.

Including phase and amplitude fluctuations reduces Drude peak widths.

Hump position shifts to lower frequency with increased doping, matching observations.

Abstract

An improved version of SU(2) slave-boson approach is applied to study the in-plane optical conductivity of the two dimensional systems of high Tc cuprates. We investigate the role of fluctuations of both the phase and amplitude of order parameters on the (Drude) peak-dip-hump structure in the in-plane conductivity as a function of hole doping concentration and temperature. The mid-infrared(MIR) hump in the in-plane optical conductivity is shown to originate from the antiferromagnetic spin fluctuations of short range(the amplitude fluctuations of spin singlet pairing order parameters), which is consistent with our previous U(1) study. However the inclusion of both the phase and amplitude fluctuations is shown to substantially improve the qualitative feature of the optical conductivity by showing substantially reduced Drude peak widths for entire doping range. Both the shift of the hump position to lower frequency and the growth of the hump peak height with increasing hole concentration is shown to be consistent with observations.